(1) Field of the Invention
The present invention relates to a system for studying, identifying, and characterizing temperature gradients within a volume of water.
(2) Description of the Prior Art
In order to use acoustics and weak scattering theory to determine the temperature field of a given volume of water, source/receiver pairs of transducers must be located at a known distance from the area to be studied and also must be aligned at a specific angle with respect to each other and the overall coordinate system. Laboratory systems tend not to be practical for field studies because the physical structure of the laboratory system interferes with the environment being studied. Also, the physical size of the components often do not make them practical for deployment by one person. Another disadvantage with laboratory systems is the presence of ground loops in the single shielded BNC cables which are used in the laboratory. When these cables are used in the ocean, ground loops occur because the internal circuit of the transducer is grounded in two places, first at the supporting electronics, and also to earth ground through the outer metal casing of the transducer.
A wide variety of structures have been used in the prior art to deploy sound devices, including acoustic transducers and hydrophones, in a variety of environments including underwater environments. For example, U.S. Pat. No. 3,176,263 to Douglas illustrates a system for measuring and recording the size and shape of solid objects. The Douglas system includes a plurality of microphones placed about and focused on an area of interest. However, Douglas lacks any disclosure of a framework for positioning the microphones.
U.S. Pat. No. 3,444,511 to Morrow discloses an array of transducers supported by a framework formed from a number of hollow plastic tubes. As shown in FIG. 1 of the Morrow patent, the transducers are mounted about the periphery of the framework. U.S. Pat. No. 3,742,540 to Hill et al. shows a passive sonar array mounting and recovery apparatus in which a plurality of transducers are mounted on the ends of hollow metal tubes that are interconnected into a framework.
U.S. Pat. No. 4,152,690 to Veatch discloses an apparatus for mounting an acoustic transducer in connection with a boat to allow the transducer to be moved about beneath the water and thereby scan more than one direction. The apparatus comprises a flexible control cable with a device which actuates it fastened to the cable's upper end. Fastened to the lower end is a pivot mechanism which converts the action of the control cable to a pivotal movement. The pivot mechanism holds a transducer support mount such that the action of the control cable pivots the transducer support mount, preferably, in a vertical plane. The pivot mechanism is connected with the boat such that the pivot mechanism and the transducer it holds are held beneath the water, and preferably, such that the transducer mount can be rotated 360 degrees about the vertical axis, as in a substantially horizontal plane.
U.S. Pat. No. 4,453,238 to Van Buren discloses an apparatus for determining the phase sensitivity of hydrophones. The apparatus includes a frame having a mounting hanger depending therefrom for holding a hydrophone beneath the surface of the water.
U.S. Pat. No. 4,881,210 to Myers et al. discloses another tubular support frame for a transducer that is to be placed in the water. Another frame arrangement is shown in U.S. Pat. No. 4,928,915 to Havins. In this arrangement,a transducer is pivotally mounted at the end of a hollow tube.
U.S. Pat. No. 5,022,012 to Godfrey et al. discloses an acoustic sensing arrangement in which a plurality of hydrophones are mounted at the ends of tubular support arms.
None of these patents however teach the use of a portable temperature gradient measurement apparatus.